I think most people would agree that regardless of one's feelings on the matter, patch notes for a game are not the appropriate venue for this sort of thing. Seems like Valve did the right thing here.
Wouldn't a blog post or a social media post be a more appropriate place for something like that, given the larger focus on interaction and outreach on those, versus something that is generally (in my experience) just used to list a bunch of changes between two versions of software?
That said, I agree with Valve that there really shouldn't be a place for harassment or really toxic behavior on the platform, at least when it's possible to limit it. Interpretations of what counts and what doesn't might vary, but this seems like a decent example of moderation action.